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Original ArticleOpen Access
Molecular Diagnosis of Prader-Willi Syndrome
Pangkanon S 
Background : Prader-Willi syndrome (PWS) is characterized by neonatal hypotonia and feed-
ing problems in infancy, developmental delay, hyperphagia with obesity, short stature, hypogonadism,
characteristic facial appearance, and behavior problems. The diagnosis of PWS is based on clinical
findings that change with age. PWS has proved to be a difficult condition to recognize with the diag-
nosis often being delayed until later childhood or even adulthood. Therefore, a molecular testing for
PWS is needed to confirm the diagnosis.
Objective : To study the clinical features of Prader-Willi syndrome patients and confirm
diagnosis by molecular testing.
Material and Method : Eighteen Prader-Willi syndrome patients who were diagnosed be-
tween March, 1997 and February, 2002 at the Genetic Unit, Queen Sirikit National Institute of Child
Health, Bangkok. Peripheral blood lymphocytes were obtained and cultured using the standard tech-
nique for chromosome analysis. For fluorescence in situ hybridization (FISH) studies, the specific DNA
probes for loci small nuclear ribonucleoprotein polypeptide N (SNRPN) were used to detect deletion.
Non-deleted cases were confirmed to have PWS by methylation analysis.
Results : The diagnosis of eighteen PWS patients was confirmed by FISH using DNA probes
for loci SNRPN demonstrating a deletion of chromosome 15q 11-q 13 in fourteen cases (77% ). Four
cases (23%) were confirmed to have PWS resulting from maternal uniparental disomy by demonstrating
exclusively maternal specific DNA methylation patterns.
Conclusion : The clinical diagnosis of PWS should be confirmed by molecular testing espe-
cially in the infancy period to avoid needless invasive diagnostic testing.
Key word: Prader-Willi Syndrome, Fluorescence in Situ Hybridization, Uniparental Disomy, Methy-
lation Study
ing problems in infancy, developmental delay, hyperphagia with obesity, short stature, hypogonadism,
characteristic facial appearance, and behavior problems. The diagnosis of PWS is based on clinical
findings that change with age. PWS has proved to be a difficult condition to recognize with the diag-
nosis often being delayed until later childhood or even adulthood. Therefore, a molecular testing for
PWS is needed to confirm the diagnosis.
Objective : To study the clinical features of Prader-Willi syndrome patients and confirm
diagnosis by molecular testing.
Material and Method : Eighteen Prader-Willi syndrome patients who were diagnosed be-
tween March, 1997 and February, 2002 at the Genetic Unit, Queen Sirikit National Institute of Child
Health, Bangkok. Peripheral blood lymphocytes were obtained and cultured using the standard tech-
nique for chromosome analysis. For fluorescence in situ hybridization (FISH) studies, the specific DNA
probes for loci small nuclear ribonucleoprotein polypeptide N (SNRPN) were used to detect deletion.
Non-deleted cases were confirmed to have PWS by methylation analysis.
Results : The diagnosis of eighteen PWS patients was confirmed by FISH using DNA probes
for loci SNRPN demonstrating a deletion of chromosome 15q 11-q 13 in fourteen cases (77% ). Four
cases (23%) were confirmed to have PWS resulting from maternal uniparental disomy by demonstrating
exclusively maternal specific DNA methylation patterns.
Conclusion : The clinical diagnosis of PWS should be confirmed by molecular testing espe-
cially in the infancy period to avoid needless invasive diagnostic testing.
Key word: Prader-Willi Syndrome, Fluorescence in Situ Hybridization, Uniparental Disomy, Methy-
lation Study
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